A laminated core for a stationary induction apparatus, such as a transformer or a reactor, has usually been formed from high-grade silicon steel sheets which contribute to energy and resource saving. Another material has recently been developed for use in the manufacture of an iron core for a stationary induction apparatus. It is a magnetic thin strip which enables a reduction in the electrical loss of the core to 20 to 80% of the electrical loss of a silicon steel sheet core.
The construction of these iron cores will be described with reference to FIGS. 1 and 2. In FIG. 1, 1a to 1d indicate silicon steel sheets, and in FIG. 2, 2a to 2d designate thin magnetic steel sheets cut from, for example, a thin amorphous magnetic strip, thin ferronickel strip or thin quenched ferrosilicon strip. 1a and 1b, or 2a and 2b are leg members, and 1c and 1d, or 2c and 2d are yoke members connecting the leg members 1a and 1b, or 2a and 2b. The core members 1a to 1d, or 2a to 2d are laminated with a minimum joint clearance to form a laminated core for a stationary induction apparatus.
The laminated core composed of silicon steel sheets as shown in FIG. 1 can be efficiently produced, since it is easy to obtain a desired shape. It is, however, very difficult to obtain a laminated core having a small loss, since it is presently difficult to expect any further improvement in the magnetic properties of silicon steel sheets.
It is easy to obtain a laminated core having a small loss from thin amorphous magnetic steel sheets as shown in FIG. 2, since they ensure a small electrical loss. A further improvement in their properties can be expected. A thin magnetic strip is produced by cooling hot molten material rapidly as it is blown against a roller or the like moving at an ultrahigh speed. This method involves a lot of technical difficulty, and presently enables the production of only a magnetic core material having a thickness of, say, 100 .mu.m and a width of, say, 2 inches. The production of a laminated core from this material involves a great deal of difficulty.
It has hitherto been impossible to obtain an inexpensive laminated core for a stationary induction apparatus having a small electrical loss if only either silicon steel sheets or thin amorphous magnetic strips are employed. The former material has the disadvantages of failing to achieve a satisfactory reduction in electrical loss, while the latter has the disadvantage of being very low in workability.